The invention relates to methods and apparatus for decontaminating solid materials, in particular solid materials in particulate form.
There is an ever-increasing need for efficient and effective methods and apparatus to remove contaminants from soil, sand and other solid materials. In particular, toxic organic substances such as petroleum hydrocarbons and various derivatives thereof have been relatively intractable using known methods for treatment of solid materials.
The utility of ozone or hydrogen peroxide as oxidizing agents for use in the treatment of aqueous waste solutions and other contaminated waters, to remove certain types of organic pollutants, is known. For example, U.S. Pat. No. 4,395,337 to Ciepela describes treatment of brackish water, wherein residual oil is stripped by treatment with ozone. U.S. Pat. No. 4,230,571 to Dadd and U.S. Pat. No. 4,504,445 to Walz describe treatment of water, wherein ozone is generated by ultraviolet radiation; in addition, Dadd notes that the ultraviolet radiation may act as a catalyst for disinfecting and oxidizing action by the ozone. U.S. Pat. No. 4,416,786 to Knorre et al. and U.S. Pat. No. 4,591,443 to Brown et al. similarly describe the use of hydrogen peroxide in the treatment of waste water.
The reactions of ozone or hydrogen peroxide with waste water are quite complex and to date are not completely understood. It is generally recognized, however, that the hydroxyl radical is an important intermediate. The hydroxyl radical functions both in the direct oxidation of organic contaminants and in the generation of additional radicals for participation in further reactions. It is known that hydroxyl radicals are formed by exposure of ozone or hydrogen peroxide to ultraviolet light (&lt;400 nm).
U.S. Pat. No. 4,792,407 to Zeff et al. describes a method of oxidizing organic contaminants in aqueous solutions which comprises using, in combination, ozone, hydrogen peroxide and ultraviolet radiation. Zeff, et al., discloses exposing contaminants to ozone either subsequently to or simultaneously with exposure to UV and hydrogen peroxide. Addition of hydrogen peroxide to the UV/ozone combination in such aqueous systems is reported to result in an increased efficiency of oxidation.